Saturday, April 9, 2016

The Impact of Enrolment in Methadone Maintenance Therapy on Initiation of Heavy Drinking among People Who Use Heroin

BACKGROUND:

There
is equivocal evidence regarding whether people who use heroin substitute heroin
for alcohol upon entry to methadone maintenance therapy (MMT). We aimed to
examine the impact of MMT enrolment on the onset of heavy drinking among people
who use heroin.

METHODS:

We
derived data from prospective, community-based cohorts of people who inject
drugs in Vancouver, Canada, between December 1, 2005, and May 31, 2014.
Multivariable extended Cox regression analysis examined the effect of MMT
enrolment on the onset of heavy drinking among people who used heroin at
baseline.

RESULTS:

In total,
357 people who use heroin were included in this study. Of these, 208 (58%)
enrolled in MMT at some point during follow-up, and 115 (32%) reported
initiating heavy drinking during follow-up for an incidence density of 7.8
events (95% CI 6.4-9.5) per 100 person-years. The incidence density of heavy
drinking was significantly lower among those enrolled in MMT at some point
during follow-up compared to those who did not (4.6 vs. 16.2).
MMT enrolment was not significantly associated with time to initiate heavy
drinking (adjusted relative hazard after
adjustment for relevant demographic and substance-use characteristics. Age and
cannabis use were the only variables that were independently associated with
the time to onset of heavy drinking.

CONCLUSION:

In
this study, MMT enrolment did not predict heavy drinking and may even appear to
decrease the initiation of heavy drinking. Our findings suggest younger age and
cannabis use may predict heavy drinking. These findings could help inform
on-going discussions about the effects of opioid agonist therapy on alcohol
consumption among people who use heroin.